A Streptococcus suis LysM domain surface protein contributes to bacterial virulence

作者：Wu, Zongfu; Shao, Jing; Ren, Haiyan; Tang, Huanyu; Zhou, Mingyao; Dai, Jiao; Lai, Liying; Yao, Huochun; Fan, Hongjie; Chen, Dai; Zong, Jie; Lu, Chengping^*

来源：Veterinary Microbiology, 2016, 187: 64-69.

DOI：10.1016/j.vetmic.2016.03.017

• Streptococcus suis
• LysM domain
• Bacterial virulence
• Iron

Streptococcus suis (SS) is a major swine pathogen, as well as a zoonotic agent for humans. Numerous factors contribute to SS virulence, but the pathogenesis of SS infection is poorly understood. Here, we show that a novel SS surface protein containing a LysM at the N-terminus (SS9-LysM) contributes to SS virulence. Homology analysis revealed that the amino acid sequence of SS9-LysM from the SS strain GZ0565 shares 99.8-68.7% identity with homologous proteins from other SS strains and 41.2% identity with Group B Streptococcal protective antigen Sip. Immunization experiments showed that 7 out of 30 mice immunized with recombinant SS9-LysM were protected against challenge with the virulent GZ0565 strain, while all of the control mice died within 48 h following bacterial challenge. In mouse infection model, the virulence of the SS9-LysM deletion mutant (Delta SS9-LysM) was reduced compared with the wild-type (WT) strain GZ0565 and SS9-LysM complemented strain. In addition, Delta SS9-LysM was significantly more sensitive to killing by pig blood ex vivo and mouse blood in vivo compared with the WT strain and SS9-LysM complemented strain. In vivo transcriptome analysis in mouse blood showed that the WT strain reduced the expression of host genes related to iron-binding by SS9-LysM. Moreover, the total free iron concentration in blood from infected mice was significantly lower for the Delta SS9-LysM strain compared with the WT strain. Together, our data reveal that SS9-LysM facilitates SS survival within blood by releasing more free iron from the host. This represents a new mechanism of SS pathogenesis.

• 出版日期2016-5-1
• 单位南京农业大学